Ex vivo human placental transfer and the vasoactive properties of hydralazine

OBJECTIVE: The purpose of this study was to determine the placental transfer and fetal vascular effects of hydralazine in an ex vivo human placental system. STUDY DESIGN: Nine placentas from uncomplicated term vaginal or cesarean deliveries were studied by means of the ex vivo single-cotyledon perfusion system. Antipyrine was used for the reference compound in the determination of the clearance index of hydralazine. Fetal vascular effects of hydralazine were determined by the effects on the perfusion pressure of the fetal artery in a constant-flow open system. Variations in fetal pressure were analyzed with the 1-sample Student t test. RESULTS: The clearance index of hydralazine ranged from 0.61 +/- 0.18 to 0.73 +/- 0.14. The accumulation of hydralazine in the recirculated fetal compartment was linear in relationship to the maternal concentration. Fetal pressure changes were noted in 6 of the 9 placentas, or 66.6%. The mean change in pressure was -4.1 +/- 4.4 mm Hg (P=.0231). CONCLUSIONS: Hydralazine readily crosses the ex vivo human placental perfusion system.